I. Field of the Invention
This invention relates generally to a prosthesis for the repair of hernias, and more particularly to an improved hernia repair patch, deliverable in a rolled form through a trocar in an endoscopic procedure and which deploys, when unconstrained, to a somewhat planar configuration.
II. Discussion of the Prior Art
In U.S. Pat. No. 5,824,082, I disclose a hernia repair patch comprising a single strand, closed loop, wire frame made of a shape memory alloy on which is attached a prosthetic mesh. That device was intended for deployment through a trocar in the course of an endoscopic hernia repair procedure. It was found that this prosthesis was somewhat difficult to deliver through a trocar of a sufficiently small diameter felt appropriate for use in typical endoscopic hernia repair surgery.
I later learned that a multifilar cable of Nitinol® strands as the frame allowed a more compact device when rolled for insertion, via a cannula, and this improvement is described in currently pending application Ser. No. 11/431,171, filed May 10, 2006 (published application US 2007/0265710 A1). That device has been commercialized as the REBOUND hernia repair patch available from Minnesota Medical Development, Inc. of Minnetonka, Minn.
In very few cases, upon patient follow-up, x-rays revealed instances where strands comprising the cable frame had broken, but without any harm whatsoever to the patients. It has been theorized that the breakage may have been as result of fatigue due to stresses on the frame induced by body motion and flexures following the complete integration of the hernia patch into the surrounding tissue by normal tissue in-growth. Even though the observed instances of frame breakage have been small and have not resulted in any adverse patient outcomes, to alleviate any potential concern by surgeons, patients or regulatory authorities, I have now conceived of a solution that should avoid stress-induced fractures in hernia patch frames.